An organic light-emitting diode (OLED) array substrate comprises a plurality of sub-pixels, and each sub-pixel has an organic light-emitting diode which can emit light of a specific color. FIG. 1 illustrates a structure of an existing organic light-emitting diode comprising an anode 1, a hole injection layer 2 (HIL), a hole transport layer 3 (HTL), a light-emitting layer 4 (EML), an electron transport layer 5 (ETL), an electron injection layer 6 (EIL) and a cathode 7 which are provided on a base substrate 9 (usually made of glass) sequentially.
The light-emitting layer is a core of the organic light-emitting diode, and made of a host material and a guest material doped in the host material. A highest occupied molecular orbital (HOMO) energy level of the host material is greater than a HOMO energy level of the guest material, while a lowest unoccupied molecular orbital (LUMO) energy level of the host material is less than a LUMO energy level of the guest material; and thus, when an electron and a hole are transported to the light-emitting layer, an exciton (an excited state molecule) is generated in the guest material. When the exciton falls back to a ground state, energy is released in a form of light, that is, light is emitted; a color of the light can be controlled by selecting the host material and the guest material.
In the light-emitting layer, the exciton has two excited states, a singlet state and a triplet state; time that a singlet state exciton falls from the excited state back to the ground state is short, so energy can be released in the form of light, and light is emitted; but a process of a triplet state exciton directly falling from the excited state back to the ground state is limited, and a relaxation time is long, so energy may be released in a non-light form (such as thermal energy, vibrational energy, etc.), resulting in lower luminous efficiency; and especially for a fluorescent light-emitting layer, there is no spin-orbit coupling unlike a phosphorescent light-emitting layer, so the triplet state exciton cannot emit light, resulting in that a theoretic luminous efficiency thereof is merely 25% (a generating ratio of the singlet state exciton to the triplet state exciton is 1:3).
Studies show that, the triplet state excitons can quench each other when energy can be released in the form of light, such that a luminous efficiency of the triplet state excitons is improved. In order to realize quenching between the triplet state excitons, it is necessary to add an “exciton blocking layer” in contact with the light-emitting layer in the organic light-emitting diode, and a HOMO energy level and a triplet state energy level of the layer cannot be less than the HOMO energy level and the triplet state energy level of the host material of the light-emitting layer; in this way, the triplet state excitons are limited in the light-emitting layer, the possibility of quenching among the triplet state excitons is increased, and the luminous efficiency is improved.
Inventors find that there are at least such problems in the prior art as follows: in an organic light-emitting diode array substrate, many layers are formed by a vapor deposition process, and the layers of different materials are fabricated by different vapor deposition devices (e.g., a vapor deposition chamber), respectively, so, if an exciton blocking layer is to be added, a corresponding vapor deposition device shall be added too, resulting in complex fabricating device and high cost; if no exciton blocking layer is provided, the luminous efficiency of the organic light-emitting diode is relatively low.